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Ordinary Shares - Additional Information (Details) ¥ / shares in Units, $ / shares in Units, ¥ in Thousands | 1 Months Ended | 12 Months Ended |  |  |  |
--- | --- | --- | --- | --- | --- | ---
Mar. 31, 2018 CNY (¥) Vote shares | Dec. 31, 2019 CNY (¥) shares | Dec. 31, 2018 CNY (¥) shares | Dec. 31, 2019 $ / shares | Dec. 31, 2018 $ / shares | Aug. 29, 2018 USD ($) | Sep. 18, 2015 $ / shares shares | Sep. 18, 2015 ¥ / shares shares
Ordinary Shares [Line Items] |  |  |  |  |  |  |  |
Ordinary shares, shares authorized |  |  |  |  |  |  | 1,000,000,000 | 1,000,000,000
Ordinary shares, par value | (per share) |  |  |  |  |  |  | $ 0.00005 | ¥ 0.0003
Ordinary shares, shares issued |  |  |  |  |  |  | 1 | 1
Proceeds from initial public offering, net of issuance cost of 80,128 | ¥ | ¥ 1,109,517 |  | ¥ 1,109,517 |  |  |  |  |
Stock issuance costs | ¥ | ¥ 80,128 |  | ¥ 80,128 |  |  |  |  |
Ordinary shares, shares outstanding | 4,329,000 |  |  |  |  |  |  |
American Depository Shares |  |  |  |  |  |  |  |
Ordinary Shares [Line Items] |  |  |  |  |  |  |  |
Ordinary shares newly issued | 16,478,275 |  |  |  |  |  |  |
Number of shares repurchased |  | 1,297,363 | 1,127,055 |  |  |  |  |
Class A Ordinary Shares |  |  |  |  |  |  |  |
Ordinary Shares [Line Items] |  |  |  |  |  |  |  |
Ordinary shares, shares authorized |  | 796,062,195 | 796,062,195 |  |  |  |  |
Ordinary shares, par value | $ / shares |  |  |  | $ 0.00005 | $ 0.00005 |  |  |
Ordinary shares, shares issued |  | 1,830,183 | 1,818,383 |  |  |  |  |
Ordinary shares newly issued | 659,131 |  | 659,131 |  |  |  |  |
Common stock, voting right |  | Class A ordinary share is entitled to one vote |  |  |  |  |  |
Number of vote each ordinary shares entitled | Vote | 1 |  |  |  |  |  |  |
Ordinary shares, shares outstanding | 63,714 | 1,728,006 | 1,773,301 |  |  |  |  |
Authorized amount under share repurchase program | $ |  |  |  |  |  | $ 50,000 |  |
Number of shares repurchased |  | 51,895 | 45,082 |  |  |  |  |
Stock Repurchased During Period, Value | ¥ |  | ¥ 30,793 | ¥ 34,828 |  |  |  |  |
Conversion of shares |  | 6,600 |  |  |  |  |  |
Class B Ordinary Shares |  |  |  |  |  |  |  |
Ordinary Shares [Line Items] |  |  |  |  |  |  |  |
Ordinary shares, shares authorized |  | 826,389 | 826,389 |  |  |  |  |
Ordinary shares, par value | $ / shares |  |  |  | 0.00005 | 0.00005 |  |  |
Ordinary shares, shares issued |  | 826,389 | 826,389 |  |  |  |  |
Common stock, voting right |  | Class B ordinary share is entitled to seven votes |  |  |  |  |  |
Number of vote each ordinary shares entitled | Vote | 7 |  |  |  |  |  |  |
Class of each ordinary shares convertible into class A ordinary shares | 1 |  |  |  |  |  |  |
Ordinary shares, shares outstanding |  | 826,389 | 826,389 |  |  |  |  |
Class C Ordinary Shares |  |  |  |  |  |  |  |
Ordinary Shares [Line Items] |  |  |  |  |  |  |  |
Ordinary shares, shares authorized |  | 203,111,416 | 203,111,416 |  |  |  |  |
Ordinary shares, par value | $ / shares |  |  |  | $ 0.00005 | $ 0.00005 |  |  |
Ordinary shares, shares issued |  | 4,258,686 | 4,265,286 |  |  |  |  |
Common stock, voting right |  | Class C ordinary share is entitled to ten votes |  |  |  |  |  |
Number of vote each ordinary shares entitled | Vote | 10 |  |  |  |  |  |  |
Class of each ordinary shares convertible into class A ordinary shares | 1 |  |  |  |  |  |  |
Ordinary shares, shares outstanding | 4,265,286 | 4,258,686 | 4,265,286 |  |  |  |  |
Conversion of shares |  | (6,600) |  |  |  |  |  |
Series A Convertible Redeemable Preferred Shares |  |  |  |  |  |  |  |
Ordinary Shares [Line Items] |  |  |  |  |  |  |  |
Preferred stock outstanding | 954,274 |  |  |  |  |  |  |
Convertible redeemable preferred shares converted into ordinary share | 954,274 |  |  |  |  |  |  |
Series B Convertible Redeemable Preferred Shares |  |  |  |  |  |  |  |
Ordinary Shares [Line Items] |  |  |  |  |  |  |  |
Preferred stock outstanding | 826,389 |  |  |  |  |  |  |
Convertible redeemable preferred shares converted into ordinary share | 826,389 |  |  |  |  |  |  |
Series B+ Convertible Redeemable Preferred Shares |  |  |  |  |  |  |  |
Ordinary Shares [Line Items] |  |  |  |  |  |  |  |
Preferred stock outstanding | 141,264 |  |  |  |  |  |  |
Convertible redeemable preferred shares converted into ordinary share | 141,264 |  |  |  |  |  |  |

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